1. Technical Field
The present invention relates to a charging time estimation device and a charging time estimation method, which estimate the time required for charging a secondary cell. In particular, the present invention relates to a charging time estimation device and a charging time estimation method for a secondary cell that is charged by receiving a constant current charging and a constant voltage charging from a charger.
2. Background Art
Conventionally, in electric-powered vehicles such as electric vehicles or plug-in hybrid vehicles, Li-ion cell with large capacity is mounted as a drive battery. In general, Li-ion cell performs a constant current-constant voltage charging (CCCV charging) in which a constant current charging (CC charging) having a constant current value is performed when the cell voltage is low and a constant voltage charging (CV charging) having a constant voltage value is performed when the cell voltage is increased to a predetermined value.
For example, Japanese Patent No. 4946749 discloses a technique to prevent overcharge when charging a battery, using a configuration to include a charging rate detection means that detects the charging rate of the battery at the start of constant current control when a constant current-constant voltage charging is performed, an elapsed time measuring means that measures the elapsed time from the start of the constant current control, a time-out setting means that sets the time-out time of the constant current control based on the charging rate detected by the charging rate detection means and a current cut-off means that cuts off the current supplied to the battery when the elapsed time measured by the elapsed time measuring means exceeds the time-out time set by the time-out setting means in the constant current control.
When charging the battery (secondary cell) in the above-described electric-powered vehicles or the like, it takes time to finish the charging. Accordingly, it is intended to improve usability by estimating the time required for charging and displaying the estimated time. The value of current or voltage that is supplied to the secondary cell or the cell capacity (maximum cell capacity or remaining cell capacity) or the like is used to estimate the time required for charging. However, the current or voltage that is supplied during charging is varied depending on the magnitude, etc., of the internal resistance in the secondary cell and the value of the maximum cell capacity is reduced due to the cell deterioration or the like. Accordingly, the charging time estimation method according to the related art has a problem that the estimation accuracy of the charging time is lowered.
The present invention has been made in view of the above-described problems of the related art and an object thereof is to improve the estimation accuracy of the charging-required time for a secondary cell.